1. Field of the Invention
The present invention is related to a method and apparatus for frame synchronization in data transmission. The method and apparatus according to the present invention are used for a high speed transmission of PCM signals in a data communication network.
2. Description of the Related Arts
In the prior art frame synchronization method, the detection of frame synchronization is carried out by successively shifting the frame synchronization pattern by one clock cycle. Accordingly, for example, the detection and identification of the frame synchronization pattern should be carried out, in the case where three groups of data of 50 Mbps are 3-multiplexed to form data of 150 Mbps, within one clock period of 150 Mbps. In such a short period, i.e., at such a high speed, it is difficult to carry out frame synchronization pattern detection reliably.
In order to reduce the speed requirement of the operation, another method has been proposed in which a latch portion, parallel synchronization detection portion, and data separation portion are provided. In this method, since the data is converted into eight groups of parallel data, latched every 8 bits, and detection of frame synchronization pattern is carried out per latch period, the speed requirement of the operation is reduced by one-eighth in comparison with the above-described prior art method.
However, since the number of frame synchronization pattern detection portions is required to correspond to the number of frame synchronization patterns for multiplexing, the scale and complexity of the circuits of the apparatus tends to be increased. Such an increase of the scale and complexity of the circuits of the apparatus is disadvantageous.